Automatically variable air supply control for oil burners



Get. 18, 1949.

J. A. LOGAN AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERSOriginal Filed May 24, 1946 5 Sheets-Sheet i INVENTOR Joszpfl Al osmv BYATTORNEYS Oct. 18, 1949. J. A. LOGAN 2,485,206

. AUTOMATICALLY VARIABLE AIR SUPPLY I CONTROL FOR OIL BURNERS OriginalFiled May 24, 1946 5 Sheets-Sheet 2 INVENTOR JosEPHALoGA/V ATTORN EYSOct. 18, 1949. J. A. LOGAN 85,

AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Original FiledMa 24, 1946 s Sheets-Sheet s INVENTOR \TOSEPII A .Z 06/44 v TTORNEYSOct. 18, 1949. J. A. LOGAN 2,485,206

AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Original FiledMay 24, 1946 5 Sheets-Sheet 4 INVENTOR JASEPHA Loan N ATTORN EYS Oct.18, 1949. J. A. LOGAN 2,

' AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL *FOR OIL BURNERS 5Sheets-Sheet 5 Original Filed May 24, 1946 INVENTOR Jon/w A Loan/v JMATA/VD 51W Rw JEN/1m BY 51: T7706 Q Y/ Z ATTORNEYS Patented Oct. 18, 1949AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Joseph A.Logan, Hadley, Mass., assignor to G1]- bert & Barker ManufacturingCompany, West Springfield, Mass, a corporation of Massachusetts Originalapplication May 24, 1946, Serial No. 672,106. Divided and thisapplication October 22, 1948, Serial No. 56,028

Claims. (01. 158-28) This invention relates to improvements in oilburners, more particularly those adapted for house-heating service.

The invention has for its object the provision in an oil burner of anautomatically variable control of the air supply for the purpose ofimproving the operation of the burner by enabling greater efilciency ofcombustion to be secured during normal running intervals of operation ofthe burner, when the air fan and oil pump are running at full speed,without smoky operation during the starting and stopping intervals ofoperation of the burner, when the fan and pump are respectivelyaccelerating and decelerating.

The invention is capable oi general application for controlling the airsupplied to mix with a spray of atomized oil, irrespective of how thatspray is produced. The invention will be disclosed by way ofillustrative example, in connection with an oil burner of the type inwhich the spray of atomized oil is produced by a pressure atomizinnozzle. The application of the invention to burners having other formsof oilspray-producing means will be readily apparent from the oneexample disclosed.

This application is a division of my applicatlon Serial No. 672,106,filed May 24, 1946.

In the accompanying drawings,

Fig. 1 is a diagrammatical view of an oil burner system;

Fig. 2 is a top plan view of the oil burner as arranged in front of afurnace wall;

Fig. 3 is a rear elevational view with parts broken away and parts insection to show one form of air control mechanism embodying theinvention;

Fig. 4 is a fragmentary cross sectional view taken on the line 4-4 ofFig. 3 and showing one form of centrifugal clutch for use in the drivingtransmission between the motor and pump;

Fig. 5 is a diagrammatical view of the fuel supply system including thepressure regulating of a different form of burner, certain parts beingbroken away and in section to show an air control valve on thepressureside of the fan;

Fig. '12 is a rear elevational view of the burner of Fig. 11; and

Fig. 13 is a fragmentary sectional view taken on the line l3--l3 of Fig.12.

Referring to the diagram of Fig. 1, l indicates an electric motor with atransmission 2 to drive an air supplyfan 3 and an oil supply pump 4. Thefan 3 blows air at a pressure of usually less than a pound per squareinch through tube 5 to mix with oil atomized at a very much higherpressure, for example one hundred pounds per square inch, and issuingfrom a nozzle 6. The air and oil mix and burn to make the flame in acombustion chamber of a heater having a front wall I. The oil is drawnfrom-a supply tank 8 through a pipe 9 by pump 4, and delivered through apipe l0 and a pressure regulating valve 1 II to a pipe l2 the outlet endof which is connected to the nozzle 6. This valve II is set to maintaina constant oil pressure in pipe l2 according to whatever pressureisneeded to enable the atomizing nozzle 6 to operate with good atomizingefficiency. The valve H which is shown schematically in Fig. 5,by-passes excess oil by a pipe Hi, to the inlet side of pump 4, to

keep the atomizing pressure constant in pipe l2,

at a value determined by hand adjustment of screw it to vary the forceof a spring l5 which bears on the head of valve l6 and tends to hold thelatter and an outlet valve I! closed. The pump 4 works at constant speedand is capable of pumping oil at a greater'rate than is needed by nozzle6, the excess being by-passed through pipe [3. The arrangement suppliesoil to the atomizing nozzle at a constant pressure predetermined byadjustment of screw it, no matter what size nozzle may be used, within aconsiderable -range of nozzle sizes, each formed for a predetermined oilconsumption rate. The rate of air supply is changed by an adjustableshutter or disc valve which is shown, in other figures to be explainedand which may control either the inlet or the outlet of the fan. Theshutter is adjusted when it is desired to change the air-oil ratio forthe mixture makingthe flame.

Such a burner system, indicated in Fig. 1, having the general nature asexplained, is well known. The type of burner having this general nature,is one of the types that may be improved by this invention. Itselectrical thermostat control T is merely indicated in Fig. 1, becauseit is so well known that it will be understood by recital of its 7function, which is to start the motor and ignition system when heat isneeded, keep the burner running until the need is satisfied, and thenstop the burner until heat is again needed, all automatically. Theignition system is represented by the electrodes I8 positioned adjacentnozzle 6. The ignition system may be turned on and off with the motorbut should at least be on when starting the burner. It is generally trueof this burner, just mentioned, that it is easy to get a clean oil flreat all times by providing a thin mixture at all times for the flame inthe combustion zone. A thin mixture is one with more air than is neededto burn the oil in the mixture. A clean fire made in this easy way isknown to be expensive. It does not burn the oil economically in anyheating plant. The economical way to burn the oil is in a mixture havinga precise and eflicient air-oil ratio, one depending on the character ofthe oil. The air-oil ratio is usually approximated by adjusting theburner and examining the flame. Theoretically, perfection would occurwhen the flame mixture has no more air supplied to it than just enoughto burn all the air and oil in the sense that all of both enter thechemical decomposition, making the flame, to make the hot products ofcombustion. Practically, a well informed man tries to make the burneroperate close to the most economical air-oil ratio, but he must makecomprises. A flame burning with a very economical air-oil ratio, whenchanged by adding a little more oil to it, will smoke and by adding alittle more air to it will begin to waste oil.

The automatic operation is of great importance in the home heatingplant. This general type of burner is one that is completely shut downbetween heating intervals. It usually operates intermittently even invery cold weather. The plan is to maintain approximately even housetemperature by intermittent heating operations. There are many separateheating intervals each day and a great many over all the days of a fullheating season. Then too, it is common to use such burners with theirintermittent heating operations, for domestic hot water heating plants al the year round. For each of the burner operations or cycles forheating, there is one starting and one stopping operation. Both areshort operations or intervals of but a few seconds. Should the burnersmoke only a little, in either of these short operations, it is likelyto be overlooked. as is also the fact that the great number of suchshort smoking intervals will add up to a lot of smoke and progressiveaccumulation of soot on the heat transfer surfaces inside a heater. Thiswill result in waste of oil no matter how efficiently it is burned inthe long heating intervals of operation. between starting and stoppingintervals. The reason will be explained later on. The problem mentionedhas received some attention and burner improvements in the past havebeen proposed to solve it. It is the problem of this invention. Thepurpose of the present improvement is to provide a better solution thanthe prior art burners provide. all things considered.

The type of burner indicated by the diagram of Fig. 1. and the troubleswith its operation just outlined. should be kept in mind when thespecific features of improvements are described as added to a burner foruse according to this invention.

One example of such a burner with the im'- provements of this inventionbuilt in, is mainly shown by the top view of Fig. 2 and rear end view ofFig. 3. These flgures indicate the motor I, the multi-vane fan 3 withcustomary vanes I 9, the

side extension 20 of the fan casing with a plurality of air inlet ports2| of ample aggregate area, the oil pump 4 with inlet 9, the transformer22 for the ignition system to be turned on and oil? with the motor, thepressure regulating valve H with regulating screw I4, its inlet pipe l0and by-pass l3 to pump 4, and the air tube 5 with the oil atomizingnozzle 6 mounted centrally in it near the end, as indicated in Fig. 2and fed by pipe l2. The parts so far mentioned are well known and needno detailed description because they have been generally available indifferent forms on the market. The constant pressure regulating valve Il, or means to perform its function, is frequently made in various formssome of which are combined in the pump construction. The drawings show aform easy to explain for the present purpose.

The air control means of this invention is shown in one embodiment inFig. 3. It includes a valve disc or shutter 24 of annular form mountedfor movement toward and away from the circular air inlet opening 25 offan 3. This shutter is movable from a relatively wide open position,such as that shown by full lines, to another and much more restrictedposition, such as that shown by dotted lines. The dotted line positionof the shutter is that for normal operations of the burner when motor 1,fan 3, and pump 4 are moving at full speed. This normal position of theshutter may be predetermined with precision by hand-operable means to bedescribed. The shutter occupies the full line position during theinitial part of each starting operation and the final part of eachstopping operation of the burner. The shutter 24 normally occupies thedotted line position when the burner is at rest and occupies suchposition until the motor and fan attain high speed when the shutter isautomatically moved to its dotted line position by means which include acentrifugal clutch 23. Such clutch also operates during each stoppingoperation of the burner to cause the shutter to move back from thedotted line position to the full line position after the speed of themotor and fan has decreased below a predetermined and relatively highspeed.

The centrifugal clutch may be like that disclosed in my prior Patent No.1,985,934 dated J anuary 1, 1935. It includes a driving element 26,flxed to the driving portion of the transmission 2 and therefore turningwhenever the motor and fan turn. Fixed to element 26 (Fig. 4) are threedriving pins 21. These pins 2'! lie in recesses 28 in adjacent radialfaces of movable clutch shoes or segments 29. When the pins 21 arerotated they rotate segments 29. The recesses 28, permil; the segmentsto move in and out radially, while driving pins 21 continue to drivefrom one constant radial distance from the driving shaft of transmission2. The segments are biased to their innermost position by a suitablespring 30,- such as the garter spring located in circular grooves 3| inthe three segments 29. When the segments 29 are rotated at asufficiently high speed, they are thrown outwardly by centrifugal forceagainst the force of spring 30 until their circumferential surfaces 32engage the inner surface of the drum 33, the driven part of clutch 23.This occurs after the fan 3 has attained a predetermined high speed asclosely as feasible to full speed. The part 33 will then start suddenlyfrom its rest position and be driven almost instantly at the sameconstant high speed as the motor. The latter will then begin to drivethe oil pump 4 0f the positive displacement type, through -drum 33 andthe collar.

the driven portion of transmission 2 to which said clutch drum 33 iskeyed. The pump 4 is then driven at full speed without appreciabledelay. When the motor current is shut off, the tran mission 2 starts toslow down and the spring 30 moves segments 29 out of driving contactwith drum 33. Then the driven part of the clutch and pump 4 stop almostinstantly because of the heavy load of pump 4 which load is suflicientto prevent the pump from any substantial amount of coasting. The inertiaof the heavy motor rotor, which is substantial, and the inertia of theeasily turned fan rotor and driving part of the clutch cause asubstantial period of coasting of the driving part of transmission 2,after the motor current is switched off by the usual thermostat. This isthe arrangement of the centrifugal clutch element. One type ofcentrifugal clutch per se, is indicated with its brief description butsuch element may be any one of many specific kinds and many areavailable on the market, simply as centrifugal clutches.

The shutter or valve 24 has, as indicated in Fig. 3, an anti-frictionmounting in the circumferential groove of a collar 34, which is slidablymounted on the driven part of transmission 2. This collar isautomatically movable into and yield-ably held in its illustratedposition by means of a spring 35, which is coiled around the driven partof transmission 2 and acts between the hub of The collar isautomatically movable to its other position by means of a centrifugalgovernor which is driven from the driven element of the centrifugalclutch and therefore operates only after the motor and fan 9 haveacquired high speed. This governor includes a plurality of pairs oflinks each pair comprising two links 36 and 31 pivoted together at theiradjacent ends. The other end of each link 36 is pivotally connected tothe collar 34 and the other end of each link 3! is pivotally connectedto the hub of drum 33. The links are provided at their interconnectedends with weights as indicated at 38 and as is usual in governors ofthis kind. It

will be clear that the governor, when rotated at.

a sufiiciently high speed will draw hub 34 and thus shutter 24 to theright, as viewed in Fig. 3, against the force of spring 35 and reducethe passage area for air to enter the fan casing.

The inner and dotted line position of the shutter for normal operationsof the burner may be predetermined with precision by the following handoperable means. A screw 39 passes loosely through a hole in shutter 24.This screw has'a bearing inthe fan casing at each end as shown, aslotted head in an outer recess of the outer bearing, a spring 49 tobiasthe screw 39 inwardly by pressing against a pin driven through the screwall as indicated. Screw 39 can be turned with a screw driver without itsmoving lengthwise and by so doing a nut 4| on the screw can be movedback and forth. The nut 4| carries a rod 42 pinned to the nut at theleft end and having an abutment stop 43 at the right end as shown. Thisrod 42 passes loosely through an opening in shutter 24 so that theshutter when operated 'bythe centrifugal governor, may slide freelyalong rod 42 as it does along screw 39, between the full and dotted linepositions as shown in Fig. 3. The shutter will engage with stop 43 as anabutment.

It will be seen that the position of stop 43 determines the right handposition of the shutter. Stop 43 can be adjusted with precision by handturning of screw 39. Its threads are adapted for fine small precisionadjustments of nut and stop 43. The shutter has an annular rim whichcooperates with an opposite annular rim 44 of the fan casing todetermine the effectivepassage area of the air inlet opening of the fan.v

When the motor is started, the fan 3 starts therewith and accelerateswith the motor until it reaches its full and high speed. During most ofthe time of this acceleration, the shutter 24 is in the full lineposition of Fig. 3 which preferably is such that the shutter does notrestrict the fan inlet opening. Thus, in the burner starting intervalthe fan can have its maximum blast of air going through tube 5 (Fig. 1)to the combustion chamber. As the fan reaches a predetermined high speedc'lose to full speed. centrifugal clutch 23 operates to drive the oilpump 4 and it supplies a full blast of atomized oil to mix with the fullblast of air, producing a combustible mixture for ignition in thecombustion chamber. Combustion starts with a lean mixture because air isflowing past the nozzle at a. high rate at the time the pump is startedand, by the time oil is emitted from the nozzle, air is flowing at itsfull rate. It should be noted that the centrifugal governor and theshutter will remain in the full line .positions of Fig. 3, while the fanis accelerating until a speed close to full speed is reached in order toestablish a high rate of air flow to the combustion chamber. This isbecause the centrifual governor used to control the shutter 24 islocated on the driven side of clutch 23. The shu'ti ter does not startto move towards its hand-adjusted position, the dotted line position ofFig. 3, until the oil pump 4 starts to operate. Then, be-

.cause the pump is positively-acting, the full rate of oil supply isestablished, practically instantaneously, as the pump starts to turn.The centrifugal governor likewise moves to high speed position andcompresses spring 35 practically instantaneously, when the driven part33 is engaged by the driving part 26 of the clutch. Shutter 24 is movedfrom full to dotted line position as the centrifugal governor moves tohigh speed position. In that position, the shutter may be positioned bysmall increments of precision adjustment by turning screw 39 by hand.When the efflcient oil burning ratio is determined by hand adjustment,the position of that adjustment, or the position of stop 43, may beconsidered a set one.

In the stopping intervals of operation of the burner, the motor I andfan 3 coast to a stop. But, when their speed starts to slacken, clutch23 stops driving the centrifugal governor and oil pump. They dopractically no coasting. They come to a quick stop. Spring 35 of thegovernor expands to move shutter 24 into its full line position ofFig.3. This is its position for practically the whole time of thecoasting to a stop by the motor and fan. Consequently when the fan isoperating at an speeds less said predetermined high speed in thestopping interval, there is'no restriction of the air inlet passage bythe shutter. More air is supplied during the stopping intervals by thisarrangement. The shutter mechanism, in its preferred arrangement, isadapted to provide no restriction of the air inlet by the shutter, whenthe fan is movin at less than said predetermined speed and a precisionadjusted restriction of the air inlet to exactly determine the air-oilratio for eflicient oil burning, when the fan is moving at full speedduring the heating interval. 01 course substantial benefits can beattained by the same mechanism even though.

starting and stopping intervals but it is preferred to have norestriction in those intervals.

For a given size of fan and supply passage and with a shutter controlfor changing the air-oil ratio, the species of Fig. 3 has a number ofspecial advantages. It shows a desirable way to automatically providefor the maximum rate of air supply when wanted during the starting andstopping intervals and for hand adjustment to accommodate the need for aprecision air-oil ratio to make the burner work efficiently at any oneof difierent rates of oil supply during the heating intervals. The oilrate may be changed over a considerable range merely by changing thesize of the atomizing nozzle at the end of the oil suppl pipe I 2.

In the form of the invention shown in Figs. 6 and 7, a somewhat largercentral hole 46 in the annular shutter 45 provides an auxiliary airinlet for the fan casing and valve means are arranged in such opening tovary the passage area therethrough from a maximum when the motor and fanare stopped to a inimurn, when the motor and fan are travelling at highspeed. In this case, the shutter is adjustable by means of a screw 47,mounted like the described screw 39 but having a threaded engagementwith the shutter. The clutch is mounted on shaft 2 in closer proximityto the pump end of the burner than in the previous example. The drivingpart 26 of the clutch 23 is provided with a circular flange 4B, theperiphery of which is located in the circular opening 46 of shutter 45.In flange 48 are cut a number of openings 49' to provide passages to fan3 for an additional air inlet area during starting and stopping periods.For each opening 49 a centrifugally operated flap 50 (Fig. '7) one endof which is fastened to the inside of flange 48, the other end of whichis bent inwardly as by leaf spring construction and weighted as at 5|,is adapted to progressively close off the additional air inlet area asthe motor and shaft 2 gain speed. When high speed is reached and clutch23 operates the pump 4, the flaps 50 have closed off openings 49. Airthen is drawn by fan 3 only through the annular opening formed byadjustment of shutter 45 through the rod 41 as described.

In Figs. 8 and 9, a pair of shutter cups are mounted in the centralopening 46 ofthe shutter 45 to control the air flow therethrough. Theshutter is adjustable by screw 41 as in Fig. 6. The outer cup 52, keyedto the driven part of transmission 2, is provided with slotted passages53 registerin with similar passages 54 of an inner cup 55 rotatingfreely on shaft 2. Inner cup 55 has a stud 56 (Fig. 9) in its outersurface projecting through a slot 51 of cup 521. A tension spring 58anchored at one end in cup 52 at 59, and at the other end on stud 56hold the inner cup with the stud 56 at one end of slot 51. In thisposition when the shaft 2 is idle, the passages of cups 52 and 55 are inregistration. Fan 3 thus draws air through these passages until theclutch rotates the drive shaft 2. By driving shaft 2 clockwise, asviewed in Fig. 9, the outer cup 52 is driven while inner cup 55 will lagcausing the passages of outer cup 52 tobe closed. The lug portions 60 incup 55 are turned inwardly to provide resistance to the r tation ofinner cup 55. The stud 56 is forced aga nst the spring action to theother end of the slot at, then in the position of Fig. 9, closing 01fthe passages 53. The relative spacing of the two cups in Figs. 8 and 9is exaggerated for purposes of clarity. They are 8 substantially insliding relationship with just enough clearance to avoid rubbing.

In Fig. 10 an hydraulic arrangement is shown for varying the air inletto fan 3 upon actuation of the clutch mechanism. In this example, theannular valve or shutter Bl has only a small central hole therethroughjust large enough to permit shaft 2 to freely pass therethrough. Theshutter has a threaded engagement with an adlusting screw 62 which isrotatable as before to set the shutter with precision in a position,such as that indicated at A, suitable for normal operations of theburner. This screw has an unthreaded inner portion 63 which isJournalled in the inner frame portion of the fan casin and at its outerend an unthreaded portion 64 which extends through a small cylinder 65and has fixed thereon within the cylinder a piston 66. The cylinder 65is fixed as indicated to the outer frame 20. This cylinder 65 issupplied with oil under pressure through an inlet 61, which receives itin any suitable way from the outlet of pump 4 as by connection to pipel2. A compression spring 68 acting between the inner end wall ofcylinder 64 and the piston 66 urges piston 86 to the left, as viewed inFig. 10, carrying with it the shutter 6|. This increases the annularshutter opening to fan 3, when the motor is starting or stopping and nooil pressure is available in the chamber of cylinder 55. When the drivenside of the clutch, the drum 33, is engaged for running operation thpump 4 operates as described to place the oil under pressure. Thispressure of the oil in cylinder 65 pushes piston 66 to the right, asviewed in Fig. 10, against the force of spring 68 and sets shutter Bl,as in the position A of Fig. 10, in the proper relative position tosecure the desired ratio of air flow when fan 3 is operating at fullspeed durin th normal heating interval of operation. The two positionsof the shutter, line A for the running position, and lin B for thestarting and stopping position, are indicated in Fig. 10.

Another example of air control means embodying the invention, is shownin Figs. 11, 12 and 13. This example is generally similar to the otherexamples and especially to the example of Fig. 10. A difference over theother examples is that the air adjusting shutter 10, Fig. 11, to controlthe rate of the air supply to the combustion zone is on the pressure oroutlet side of the air fan rather than the inlet or low pressure side.The motor H, drives the fan 12 and oil pump 13 by a transmission similarto the one of the first example of Fig. 3 and with a centrifugal clutchin it. The transmission arrangement is the same except that the motor His between the oil pump 13 and fan 12, with its centrifugal clutchpositioned to drive the oil pump only when the motor and fan aresubstantially at their high speed, and to leave the oil pump stopped atother times. This will be understood from the first example.

In the Fig. 11 structure, the fan 12 has an unrestricted inlet at theleft of its casing and by its vanes, blows the air into annular chamber14. Stationary slanting, air directing vanes 15 with spaces between, areadapted to cause whirling of the air in spiral form, as it enters theextension 16, closed at the back and open at the front to cause feedinginto air tube 11 corresponding with tube 5 of Fig. 2. The fiat ring orhoop-shaped shutter 10 is adapted for back and forth axial adjustment,to close more or 7 less of the area of the openings between stationaryvanes and thus control the rate at which air enters the tube 11 from thefan and on its pressure side. The burner features important here asdiffering from the other example are, the position of this shutter onthe pressure or outlet side of the fan and the way of adjusting thisshutter automatically and in relation to its hand adjustment. Thisexample is similar to that shown in Fig. 10.

Referring to Fig. 13, shutter W is carried for adjustment by a yoke 18hanging from short rod 19, mounted in the spaced depending arms of asleeve 80, threaded on a screw 8|. An unthreaded portion at one end ofthis screw has a free bearing in the burner casing permitting the screwto both turn and slide axially. An unthreaded portion at the other endof screw 8! passes through a ower cylinder 82 and has fixed theretowithin the cylinder a piston 83. This cylinder at inlet opening 84 is inconstant communication by branch pipe 85 (Fig, 12) with the oil deliveryline indicated at 86 (Figs. 11 and 12), on its high pressure side fromthe pump to the atomizing nozzle 81. So whenever the oil pump isturning, the high oil pressure (the oil pressure in both examples may bea high as around one hundred pounds per square inch) is applied ashydraulic pressure on the left of piston 83 (Fig. 13) to move and holdthe screw the air tube 11. This will make it simple to get greatexactness in the quantity of air going to mix with the oil from theatomizing nozzle for the air-oil ratio in the heating interval of thisburner. The oil quantity is constant as has been explained in the firstexample. The speed of the fan 12 is constant also, as the motor speed inthese burners is constant, except in starting and stopping intervals, sothe air-oil ratio for the heating interval is constant, and 'by handadjustment in the installation work may be made constant for a highlyeflicient oil burning ratio.

This structure is adapted to automatically shift the shutter 10 to openup a much larger air passage area to the combustion zone for the fiameduring the starting and stopping intervals. Coiled pring 88 (Fig. 13)between sleeve 80 and .end wall 89 of cylinder 82 is adapted to biassleeve 80 and thus screw 8! on which it is threaded, to the left of theposition shown. When the oil pump stops, oil pressure in cylinder 82drops, and spring 88 moves shutter 18 to'the Start and stop setting asindicated by the dot dash line in Fig. 13. It is moved back to the Runsetting for the heating interval, when the oil pump starts itsoperation. For this purpose the piston in cylinder 82 is made todominate the action of spring 88 when the oil pump is operating as thiscylinder 82 contains high oil pressure acting to the left of piston 83to move it to the right and carry screw 8| against the spring 88. Theoil pump is driven, only when the motor and fan are at top speed, by acentrifugal clutch in the motor transmission of this burner as in thefirst example.

The result is that the operation of the burner in the-example of Figs.11 to 13 is the same as in the first example or any example where theshutter is on the inlet side of the fan, in these significant respects.During the starting and stopping-intervals a much larger air passagearea is automatically made available for the fan than the air passagearea that is available under precision adjustment during thecomparatively long heating intervals which occur between the shortstarting and stopping intervals.

It should be noted also that the structure to get this result is quitesimple. Such structure is adapted for application to existing forms ofburners already in use, to convert them to the improved form for moreeconomical operation in the use of oil. It is adapted for use in themanufacture of new burners with a little extra expense in merely addingthe new elements to make the new burner combination.

The manner of automatically changing the eifective' area of theshutter-controlled airinlet passage to vary the rate at which air issupplied by the fan to the combustion chamber to adjust the air-oilratio is both cheap and efiicient. Men accustomed to install the priorart burners are accustomed to adjust the shutter of each burner to getthe air-oil ratio for its operation. One practice is to provide enoughair to avoid smoke altogether; but a thin enough mixture to do this inthe starting and stopping intervals, will waste a lot of oil in theheating intervals. Another practice is to let the prior art burner smokejust a little but only in the starting or stopping interval or both.This will give better combustion efficiency in the heating intervalswhen checked by gas analysis instruments, but will result in sootdeposits and consequent insulation of heat transfer surfaces. Theinstallation men usually check for any smoking by simply looking at theflame but sometimes a smoke detector instrument is used. In any case,they follow the practice, when installing, of adjusting the shutteruntil they get a little smoke and then again adjusting it for justenough more air. to stop the smoke. It is a fine adjustment and has tobe made when the burner is operating at full speed at the placeinstalled and necessarily an adjustment to be made in the field and notin the factory.

Under these circumstances, consider the utility of burners containingthe present invention and furnished by a factory to the men, usuallyindependent dealers, who will install them in all kinds of heatingplants. ter with a fine adjustment to avoid smoking in the heatinginterval, that adjustment need not be compromised by further adjustingto avoid smoking in the starting and stopping intervals. The air passagearea is automatically increased during the stopping and startingintervals so much that the installing men neednever adjust the shutterto avoid smoke.

The additional air inlet area provided for use in the starting andstopping intervals should be large enough to accommodate different sizedatomizing nozzles. For any given oil pressure, the size of the orificein the nozzle determines the rate of oil supply. Assuming that thefactory furnishes a dealer with a given size burner, he may use iteither for a heating plant requiring a certain oil consumption rate orone requiring several times that given rate or any rate between. All thedealer needs to do in order to adapt the burner for the desired oil rateover a substantial range is to use an atomizing nozzle with an orificesize to determine the rate. The same burner will operate with differentsize oil When theyadjust the shutnozzles. It will be apparent that asthe oil consumption rate is increased more air is needed in order tomaintain the proper air-oil ratio. The dealer will adjust the shutter toget the economical air-oil ratio during the heating interval for a givensize nozzle. The automatic increase in air passage area for the startingand stopping intervals will be sufiicient to get the results wanted fora range of oil consumption rates. In the installation of the improvedburners, the dealers will just naturally make a more efllcientadjustment of the shutter to save oil. This saving will be made everyday the burner operates. The dealer can now confine his attention tomerely setting the air adjustment for the heating intervals. Plenty ofair is provided by simple automatic means to avoid smoke in the startingand stopping intervals. The improved burner results in very eflicientuse of oil, while maintaining a clean fire at all times.

The invention is characterized by the arrangement for automaticallyincreasing the air passage area of the fan during the starting andstopping intervals of operation of the burner. The purpose is toestablish a high rate of air flow more quickly than would otherwise bepossible during the starting interval of operation and to maintain ahigh rate of air flow longer than would otherwise be possible during thestopping interval of operation of the burner. A clean fire can be had atall times and the burner can operate at higher efificiency during itsnormal running intervals of operation because the extra air neededduring the starting and stopping intervals of operation in order toavoid smoke is provided by the means of this invention.

The invention is useful regardless of how the oil spray is produced andwhether the spray is composed wholly or only partly of oil. Theinvention has been disclosed in its most difficult application, .whereinhigh oil pressures are required for atomization of oil by pressure.Here, the load of the pump is great and it is desirable to use theclutch in the drive to the oil pump in order to unload the motor to getfaster starting of the fan and to get greater coasting of the fan afterthe motor circuit is opened. In other types of burners, the clutch inthe pump drive may not be needed and the flow of oil to the nozzle canbe otherwise controlled. However, the automatic means for increasing theair passage area during the starting and stopping intervals will havevalue, as before stated, in providing the extra air needed during suchintervals to avoid smoky operation and yet enable operation of theburner during its normal running intervals at high efiiciency.

' Having disclosed my invention, I claim:

1. An oil burner for starting, running and stopping operations underthermostatic control, comprising, an air supply fan, a casing for saidfan having an inlet and an outlet opening, an air tube connected to saidoutlet opening and through which the air for combustion is supplied, anatomizing nozzle in said tube to supply oil at a constant rate to mixwith the air supplied through said tube, a pump to supply oil to saidnozzle, a motor, driving means connecting the fan to the motor to startand stop coincidentally therewith, driving means connecting the pump tothe motor and including a centrifugal clutch operable to drive the pumponly when the motor and fan are operating at or above a predeterminedhigh speed, valve means associated with one of said openings to controlthe passage area for the flow of air to said tube, hand-operable meansfor actuating said valve means to determine a precision adjustment ofthe passage area for normal operation of the burner, yieldable means foractuating the valve means to increase the passage area, and meansoperatively connected to said clutch to operate only while the motor andfan are moving at or above said predetermined speed for actuating saidvalve means to counteract said yieldable means and decrease the passagearea to that for normal opertion of the burner.

2. An oil burner for starting, running and stopping operations underthermostatic control, comprising, an air supply fan, a casing for saidfan having an inlet and an outlet opening, an air tube connected to saidoutlet opening and through which the air for combustion is supplied, anatomizing nozzle in said tube to supply oil at a constant rate to mixwith the air supplied through said tube, a pump to supply oil to saidnozzle, a

motor, driving means connecting the fan to the motor to start and stopcoincidentally therewith, driving means connecting the pump to the motorand including a centrifugal clutch operable to drive the pump only whenthe motor and fan are operating at or above a predetermined high speed,a valve for one of said openings and movable from one position toanother to vary the effective air passage area, means tending to holdsaid valve in its position of greater passage area, hydraulic meansoperatively connected to the pump to move said valve into its positionof lesser passage area whenever the pump is in operation, andhandoperable means for adjusting said valve and predetermining withgreat accuracy its last-named position.

3. An oil burner for starting, running and stopping operations underthermostatic control, comprising, an air supply fan, a casing for saidfan having an inlet and an outlet opening, an air tube connected to saidoutlet opening and through which the air for combustion is supplied, anatomizing nozzle in said tube to supply oil at a constant rate to mixwith the air supplied through said tube, a pump to supply oil to saidnozzle, a motor, driving means connecting the fan to the motor to startand stop coincidentally therewith driving means connecting the pump tothe motor and including a centrifugal clutch operable to drive the pumponly when the motor and fan are operating at or above a predeterminedhigh speed, a valve for one of said openings and movable from oneposition to another to vary the effective air passage area, meanstending to hold said valve in its position of greater passage area,means operatively connected to the driven element of said clutch to movesaid valve into its position of lesser passage area whenever the pump isin operation, and hand-operable means for adjusting said Valve andpredetermining with great accuracy its last-named position.

4. An oil burner for starting, running and stopping operations underthermostatic control, comprising, an air supply fan, a casing for saidfan having an inlet and an outlet opening, an air tube connected to saidoutlet opening and through which the air for combustion is supplied, anatomizing nozzle in said tube to supply oil at a constant rate to mixwith the air supplied through said tube, a pump to supply oil to saidnozzle, a

motor, driving means connecting the fan to the motor to start and stopcoincidentally therewith, driving means connecting the pump to the motorand including a centrifugal clutch operable to 13 drive the pump onlywhen the motor and fan are operating at or above a predetermined highspeed, a valve for one of said openings and movable from one position toanother to vary the efiective air passage area, means tending to holdsaid valve in its position of greater passage area, and a centrifugalgovernor connected to the driven element of said clutch to be rotatedthereby and operable when rotated at or above a predetermined speed tomove said valve into its position of lesser passage area, andhand-operable means for adjusting said valve and predetermining withgreat accuracy its last-named position.

5. An oil burner for starting, running and stopping operations underthermostatic control, comprising, an air supply fan, a casing for saidfan having an inlet and an outlet opening, an air tube connected to saidoutlet opening and through which the air for combustion is supplied, anatomizing nozzle in said tube to supply oil at a constant rate to mixwith the air supplied through said tube, a pump to supply oil to saidnozzle, a motor, driving means connecting the fan to the motor to stopand start coincidentally therewith, driving means connecting the pumptothe motor and including a centrifugal clutch operable to drive the pumponly when the motor is operating at or above a predetermined high'speed, an an-- 14 nular disc valve associated with one of said openingsto control the passage area for the flow of air to said tube, said valvehaving a central opening, hand-operable means for effecting a precisionadjustment of the rim of said disc in spaced rela- REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,012,037 Drew Aug. 20, 19352,464,698 Logan Mar. 15, 1949 2,465,125 Schulz Mar. 22, 1949

